×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Contact US

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

Can the air pressure in tank be higher than the compressor outlet pressure?
3

Can the air pressure in tank be higher than the compressor outlet pressure?

Can the air pressure in tank be higher than the compressor outlet pressure?

(OP)
I am trying to simulate the performance of a compressed air energy storage system.
I have modeled the compressor using the following equation


The compressed air pressure in the tank is changing according to the following equation


The outlet pressure of the compressor is 15 bar and the maximum air pressure limit of the compressed air tank 30 bar with a constant volume. By running the simulation and supplying power to the compressor, more compressed air mass flow rate is generated and fed to the air tank and the pressure increases in the tank reaching 25 bar in my case. Can the air pressure in the tank exceeds the maximum outlet pressure of the compressor ? Is there like a non-return valve or something for that ?

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

Quote (Ameen1985)

Can the air pressure in the tank exceeds the maximum outlet pressure of the compressor ?

Did you actually do any reflective thinking before writing that?

The answer on the data provided is clearly no, otherwise you've found the answer to the worlds energy problems....

Ypour model clearly doesn't recognise the physical facts of life and therefore needs to be redesigned.

Not only will the compressor simply stall or stop flowing or lift the relief valve, but the energy required changes as the pressure rises. Maybe your formula recognises that - I can't say, but it's not a fixed thing and changes as the air pressure increases.

The only way pressure can rise in the "tank" or Pressure vessel is if you inject more mass or the temperature rises.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

What LittleInch said.

By way of example:

Some of the oil circuit breakers I used to operate had pneumatic closing mechanisms.

If the breaker's air system was in a good and tight condition and pumped itself up overnight due to air contraction in the receiver, the air pressure in the receiver would be at maximum right at sunrise.

As the mechanism box and air receiver were heated by the sun over the course of the day, the air in the receiver would expand due to insolation, but due to its being confined in the receiver the air pressure in said receiver would slightly exceed the compressor discharge pressure sometime mid-afternoon, but not usually enough to cause the receiver safety valve to blow off.

There is almost always a check or non-return valve in the piping between the compressor and the air receiver so that full receiver pressure is not continuously applied to the compressor discharge valve or valves.

Additionally, any but the smallest compressors typically have an unloading system that bleeds off the compressor discharge pressure upon shutdown, such that upon subsequent restart the compressor has no work to do and reaches full operating speed promptly.

Beyond that, it seems the OP needs to give his head a shake.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

Quote:

The only way pressure can rise in the "tank" or Pressure vessel is if you inject more mass or the temperature rises.

The OP's model doesn't understand that you can't inject more mass from a lower pressure to a higher pressure.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
FAQ731-376: Eng-Tips.com Forum Policies forum1529: Translation Assistance for Engineers Entire Forum list http://www.eng-tips.com/forumlist.cfm

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

All utility air compressors would have check valve on final discharge to prevent reverse flow when the compressor goes into unload mode.

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

They say there are no bad questions, but they're wrong.

Yes, the pressure in the tank could be higher than the compressor discharge pressure, but something other than the compressor is needed to cause that.

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

(OP)
Many thanks for your answers.
As you said, I (the OP) need to give my head a shake.
The used air receiver equation in my model doesn't depend on the compressor pressure. As more air mass flows to the air receiver, its pressure increases. Then, I found it exceeds the air compressor discharge pressure which is not possible because the compressor is responsible for charging the air into the vessel. However, I thought may be there is a mechanism, valve, or anything can allow inject more mass from a lower pressure to a higher pressure.
Thank you again for your answers.

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

Quote (Ameen1985)

However, I thought may be there is a mechanism, valve, or anything can allow inject more mass from a lower pressure to a higher pressure.

There is, it's a second compressor, or second compressor stage in a multi-stage compressor.

Good Luck,
Latexman

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

It's the one powered by Snake Oil...

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

RE: Can the air pressure in tank be higher than the compressor outlet pressure?

If you can generate enough velocity and then slow the flow there will be a pressure rise. The trouble is that you need to start with a lower pressure to generate the high velocity and then create a pressure rise when the flow is suddenly stopped. I believe this is called recompression.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members! Already a Member? Login



News


Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close